'You have learned nothing from Brexit. If you had given (David) Cameron concessions, particularly on immigration, the Brexit vote - I have to admit - would never, ever have happened.

'And yet the lesson you take is that you are going to centralise and move on to this very worrying, undemocratic union.'

The commission president seized on a recent economic uptick by EU states to say many of its difficulties were being overcome

Yesterday Theresa May was mocked by MEPs as 'out of her depth' after refusing to speak at the European parliament.

Philippe Lamberts, a Belgian who co-chairs the Green group, said the PM was at the 'very edge of her skills' and it was 'starting to show'.

He also jibed that Mrs May would have only 'further weakened the UK's position' if she had agreed to appear at the parliament.

The vicious barbs came as it was confirmed that the next round of Brexit talks will take place on September 25 - slightly later than had been expected.

The next round of talks between Brussels' chief negotiator Michel Barnier and Brexit Secretary David Davis had been due to begin on Monday in Brussels. Last week a row erupted when EU minutes revealed disparaging comments about the British team.

It is thought that Mrs May intends to make a major intervention before that date, potentially on September 21.

Mr Farage made sure his union flag was in pride of place when he arrived in the chamber today

The PM (pictured in Downing Street today) has signed up to discuss her plans for Brexit with leaders of the main groups in the EU parliament